got also a HU series tv and tried to get exlink to work. For now, everything works fine, except the power on command.
It seams that the device disables the serial interface if its powered off. Is there any way to make a standby mode on the serial interface of the tv. for example by the hidden service menue?

Thanks for the quick reply. "Samsung Instant On" is already on. Quickly Power OFF or similar is not visible there. Maybe it depends on my selected language which is german.
root would be a solution, but i´m a little bit scared to brick my device